Linux Ethernet Bridging - Apr 2020 - [Bridge] [RFC PATCH net-next] net: bridge: fix client roaming from DSA user port

When a client roams from a DSA user port to a soft-bridged port (such as WiFi
interface), the left-over MAC entry in the switch HW is not deleted, causing
inconsistency between Linux fdb and the switch MAC table. As a result, the
client cannot talk to other hosts which are on that DSA user port until the
MAC entry expires.

Solve this by notifying switchdev fdb to delete the leftover entry when an
entry is updated. Remove the added_by_user check in DSA

Signed-off-by: DENG Qingfang <dqfext at gmail.com>
---
I tried this on mt7530 and mv88e6xxx, but only mt7530 works.
In previous discussion[1], Andrew Lunn said "try playing with auto learning
for the CPU port" but it didn't work on mv88e6xxx either

I think commit 7e26bf45e4cb ("net: bridge: allow SW learn to take over HW
fdb
entries") already tried to fix this issue..

[1] https://lore.kernel.org/netdev/20200405150915.GD161768 at lunn.ch/

 net/bridge/br_fdb.c | 3 +++
 net/dsa/slave.c     | 2 --
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/net/bridge/br_fdb.c b/net/bridge/br_fdb.c
index 4877a0db16c6..46003e78f2ac 100644
--- a/net/bridge/br_fdb.c
+++ b/net/bridge/br_fdb.c
@@ -579,6 +579,9 @@ void br_fdb_update(struct net_bridge *br, struct
net_bridge_port *source,
 			/* fastpath: update of existing entry */
 			if (unlikely(source != fdb->dst &&
 				     !test_bit(BR_FDB_STICKY, &fdb->flags))) {
+				/* Remove the entry in HW */
+				br_switchdev_fdb_notify(fdb, RTM_DELNEIGH);
+
 				fdb->dst = source;
 				fdb_modified = true;
 				/* Take over HW learned entry */
diff --git a/net/dsa/slave.c b/net/dsa/slave.c
index e94eb1aac602..6133a1be1a74 100644
--- a/net/dsa/slave.c
+++ b/net/dsa/slave.c
@@ -1932,8 +1932,6 @@ static void dsa_slave_switchdev_event_work(struct
work_struct *work)
 
 	case SWITCHDEV_FDB_DEL_TO_DEVICE:
 		fdb_info = &switchdev_work->fdb_info;
-		if (!fdb_info->added_by_user)
-			break;
 
 		err = dsa_port_fdb_del(dp, fdb_info->addr, fdb_info->vid);
 		if (err) {
-- 
2.26.0

On Mon, Apr 20, 2020 at 12:19:46AM +0800, DENG Qingfang
wrote:
> When a client roams from a DSA user port to a soft-bridged port (such as
WiFi
> interface), the left-over MAC entry in the switch HW is not deleted,
causing
> inconsistency between Linux fdb and the switch MAC table. As a result, the
> client cannot talk to other hosts which are on that DSA user port until the
> MAC entry expires.
> 
> Solve this by notifying switchdev fdb to delete the leftover entry when an
> entry is updated. Remove the added_by_user check in DSA
> 
> Signed-off-by: DENG Qingfang <dqfext at gmail.com>
> ---
> I tried this on mt7530 and mv88e6xxx, but only mt7530 works.
> In previous discussion[1], Andrew Lunn said "try playing with auto
learning
> for the CPU port" but it didn't work on mv88e6xxx either
Hi Deng

We should probably first define how we expect moving MAC to work. Then
we can make any core fixes, and driver fixes.

For DSA, we have assumed that the software bridge and the hardware
bridge are independent, each performs its own learning. Only static
entries are kept in sync.

How should this separate learning work for a MAC address which moves?

    Andrew